Hello, I just want to share my experiences (and also ask a few things). I drive a Mazda 6, 2005 year, 2.0L with 141 hp. I had the car converted last year at the km-level from 102,000 to autogas. was installed a Prinsystem with flashlube (installation cost: 2,500 euros). I know (and also knew before) that with this model there are sometimes problems with the valves etc. so I do not drive in autogas operation over approx. 140km/h (approx. 4000 rpm) and avoid fully after 10,000 km (i.e. 112.000 km) I had the valve play checked on the advice of my changer at Mazda. according to Mazda everything was in order, nothing had to be set (this statement of course I have to trust). after 20,000 km (i.e. 122.000) the gas filter was changed and the gas system was checked: everything was in order. now I was at 135,000 km, i.e. I drove 33,000 km with gas. the engine is running perfectly, it is there are no problems. the gas consumption is about 10 liters. insofar I am fully satisfied with the gas system (in my beloved Mazda6)! 1. Question: when should I have the valves checked again? 2. Question: the inspection of the valves cost almost 300 euro at Mazda. (I was explained that this model is quite expensive and therefore relatively much working time). is this a normal (mazda) price? can I check the valves elsewhere and if necessary a 3.Question: what about spark plugs? should they be changed more often than in petrol operation? thank you and nice greeting!